The goal was to identify the latter, hook them, and then reel them in, turn them into “travelers.” Once a traveler took that all-important step out of fantasy and into the real world, his behavior went from the merely immoral to the overtly criminal.When they delivered themselves for the promised rendezvous, instead of meeting a mother and her young daughters they would find a team of well-armed, cheerfully disgusted Delaware County police officers.He had immediately tapped her with three messages, and she had responded: The sun blazed in from the window to his back porch.J had about an hour before his wife would be home from work.As Jad, one of the policemen in the movie version, says, “We’re more like clergy than cops.”Bingo! The line popped up in a window at the top of J’s screen as soon as he logged in to the chat room.He had peeked into a number of active chats to see how many women were there, and logged on to the ones with a promising ratio.He imagined it was like a colorful lure on the surface of a pond.He was excited to see on-screen that this woman, calling herself heatherscutiepies, lived in his state, Pennsylvania, and was 39 years old.

In practice that means looking for people who potentially fit the mold—people who seem as if they might be poised to commit a crime even if they have not yet done so.

Police patrolling the precincts of sin do not often find the streets empty.

How are they to tell the difference between the casual sinner and the criminal?

Her parents sent her to Catholic schools, and her mother, a retired district judge, now jokes that she wants her money back.

Her daughter’s beat is in the vilest corners of cyberspace, in chat rooms indicating “fetish” or various subgenres of flagrant peccancy.

After months of prowling Internet chat rooms, posing as the mother of two young daughters, Detective Michele Deery thought she had a live one: “parafling,” a married, middle-aged man who claimed he wanted to have sex with her kids.